1. Field of the Invention
The present invention relates to an automatic blood analysis apparatus and method for the simultaneous automatic analysis for a plurality of parameters of whole blood. Analyses of that type include determination of parameters such as total hemoglobin, oxygen content and three known percentages based on total hemoglobin.
2. Description of the Prior Art
There are many known apparatus related to and used in the photometric determinations for constituents of blood samples. Each one of these prior art apparatus, however, suffers from at least one built-in limitation, namely, that in employing a conventional light source with filters, the same encounters drift which affects the wavelength transmitted through the specimen after a period of time of use. Consequently, readings of the instruments become progressively less reliable with the passing of time.
The photometer disclosed in U.S. Pat. No. 3,694,092 is designed to analyze for albumin and bilirubin in serum through a combination of a conventional light source and a rotating filter wheel. It transmits through the sample two wavelengths and then by multiplying the test result of the sample for one wavelength by a certain coefficient and subtracting the value obtained from the test result of the sample for the other wavelength, quantitatively analyzes the sample. An apparent improvement of this is the disclosure in U.S. Pat. No. 3,902,812 which employs three kinds of light wavelengths again obtained from a conventional light source by means of a three-segment filter wheel and in which the three wavelengths are used to eliminate the influence of two components except the one to be measured.
The closest known disclosure appears to be U.S. Pat. No. 3,972,614 to Johansen et al which again uses a conventional light source and by means of a rotating filter wheel employs two wavelengths and then transmits these wavelengths through a hemolyzed blood sample, with hemolyzing effected by ultrasonic means and without the use of a diluent. The patent teaches the measurements for the concentrations of only two constituents, namely, oxyhemoglobin and reduced hemoglobin at these two wavelengths to arrive at total hemoglobin. Consequently, the measurements do not take into account the presence of methemoglobin and carboxyhemoglobin and when either of these concentrations are present in the sample it requires that corrections be made to the results obtained by the instrument.
Other disclosures known include that of U.S. Pat. No. 3,748,044 which again uses a conventional light source and filters. It employs a cycling apparatus to cause the beam sequentially and separately to pass through each of a multiplicity of specimens during the multiple cycles of operation. It then determines the rate at which reactions take place in each of the specimens by comparing the second set of values to the first set of values previously stored in memory. The U.S. Pat. No. 3,807,877 discloses a photometer again employing a conventional light source in which the light transmitted by a reference and a sample substance is alternately measured to have an output voltage representative of the sample density, with the photometer sensitivity varied as a function of this output voltage, by scaling the output of the detector to the input power. U.S. Pat. No. 3,437,822 discloses a radiation absorption measuring device again employing a conventional light source in which the lamp supply is controlled by a feedback amplifier so as to stabilize the light source output power. U.S. Pat. No. 3,690,772 shows an apparatus again using a conventional light source by which light pulses are transmitted through at least three light ray paths at intermittent intervals so that no more than one light path is illuminated during any instant of time. The pulses of one path are used as a reference pulse and the remaining pulses filtered, aligned, and passed through the sample. Light passing through the sample and also light on the referenced paths are then directed to a single photo cell. Output signals from the photo cell are maintained steady to prevent light source intensity variations from influencing readings.
Each of these prior art devices suffers from not providing that high degree of precision of repeated readings that today's clinical market requires for the automatic measurements of parameters contained in whole blood.